While conventional mammography is an effective screening tool for breast cancer, other technologies including ultrasound may provide additional diagnostic information. When biopsy is recommended based solely on mammography, about 24% will be malignant. With the use of the information provided by the new strategies presented in this proposal, the proportion of negative biopsies may be significantly reduced. In addition, these new techniques may provide an improved understanding of the nature of the vascular architecture in a benign and malignant mass. In order to improve the detection and assessment of breast tumors, the development of a new ultrasonic flow detection system that can detect low velocity flow in small vessels, and map these vessels in three dimensions is proposed. Through our previous studies of the nature of slow flow in small vessels, a more sensitive flow detection strategy has been developed. This sensitive flow detection strategy can detect flow with a velocity of 0.8mm/s, in comparison with the limit of 2-3 cm/s for current color flow mapping systems. In addition, using three dimensional space scale analysis techniques, a three dimensional map of the vasculature will be developed using both the flow and gray scale information to achieve frame to frame vessel registration. This project will explore detailed three dimensional mapping of tumor vasculature with the ultimate goal of providing maps which: characterize normal and abnormal flow, evaluate the vasculature associated with benign and malignant tumors, and assess changes in the vascular tree during treatment. The new velocity estimation and clutter rejection strategies developed by the principal investigator, will be optimized for their use in the assessment of flow in the array of vessels within a solid mass. An existing experimental system will be modified to gather data from a three dimensional region, using a motorized single linear array. A three